Eight Vietnamese adults have tested positive for hand, foot, and mouth disease (HFMD), which is usually considered a children's infection and had killed 114 in Vietnam this year as of Saturday, the Pasteur Institute said.

The institute in the central coastal province of Khanh Hoa said the adults came from families with HFMD-infected children in central Vietnam.

Two of them are from Quang Ngai Province, to the north of Khanh Hoa, four are from Ninh Thuan, which borders Khanh Hoa to the south, and two are from Binh Thuan, which borders Ninh Thuan.

Vien Quang Mai, deputy head of the institute, said all eight people were found with Enterovirus 71, which causes the disease, but they had yet to develop signs of sickness like infected children do.

Based on the finding, Mai said some infected adults, who look completely healthy, might spread the disease farther and wider.